So far, we have seen the Lumia 630, Lumia 930, and the Lumia 530. In addition, the Lumia 730, which is codenamed as the “Lumia Tesla” is reportedly arriving later this month with Windows Phone 8.1 Update 1 out of the box. Now a new leak suggests the existence of Lumia 830, and the handset is tipped to be making its way to the AT&T network.

Microsoft was definitely expected to refresh the Lumia 820 -- as it has done with all the other handsets in that series, except for Lumia 1020, which might happen too. The Lumia 830 is internally codenamed as “Train".

Lumia ‘Train’ might as well be an AT&T exclusive, as the network juggernaut will need some new devices for the upcoming shopping season. As the HTC One (W8), which is arriving later this month, could be a Verizon exclusive.

The Lumia 820, for those that do not know, features an 8.7MP camera, 4.3-inch display, powered by a dual-core 1.5 GHz processor. The Lumia 830 will likely provide newer, faster, and better specs. We're flagging this as a "credible rumor" until more details emerge.